Performance Factors and Opportunities

To assess the advantages of the weldbonded joint, one must look at the properties of the spot weld alone, the adhesive bond alone, and compare these to the properties of the weldbonded joint. One must also be aware of the physical and environmental effects on the joint. Studies show that weldbonded joints can be stronger than joints that are only spot welded or only adhesively bonded. However, metal thickness, surface preparation, adhesive flow and cohesion, and weld quality can influence the results. 

Weldbonded aluminum joints (1-mm aluminum alloy 2036-T4) where compared with spot welded aluminum (1-mm aluminum alloy 2036-T4) and spot welded steel (1-mm steel 1010) joints.45,46 Weldbonded 2036-T4 joints made with a vinyl plastisol adhesive and with a one-part modified epoxy had a fatigue strength about twice that of the spot welded aluminum alloy and approximately the same as that of the spot welded steel. The fatigue strength of the weldbonded aluminum joints with polysufide-epoxy adhesive or with high-peel-strength epoxy adhesive is higher than that of steel spot welds alone. 

The degree of acceptance of weldbonding applications has been increasing, as the process has been understood and its mechanical properties developed.47 The principal advantages that have been claimed for weldbonding include the following. 

Fatigue endurance is enhanced compared to that of mechanical fasteners or spot welding alone, since the stress concentration factor at the joint is reduced. The adhesive layer results in a more uniform stress field around the weld nugget. 

There is improved energy absorption compared to either spot welding or adhesives bonding alone. 

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